The present invention relates to a seat comprising parts that are movable relative to one another, at least one actuator for controlling at least one moving part of the seat, and a control unit for controlling the or each actuator, said control unit comprising:
user control means for controlling a main actuator selected by a user;
tracking means for tracking the current position of the or each actuator; and
management means for managing the control of the or each actuator and adapted to ensure that no moving part of the seat reaches a forbidden region.
Such a seat may be a vehicle seat, for example, suitable for being used in particular in airliners.
For example, such a seat comprises a seat proper having hinged relative thereto a back which is surmounted by a movable headrest. In addition, a leg support is hinged to the seat proper and the leg support is extended by a sliding footrest. The seat proper itself is hinged relative to the fixed underframe of the seat.
Each moving part of the seat is driven by a respective actuator relative to some other part of the seat with which it is associated.
Means for tracking the current position of each actuator are implemented so as to be able to determine continuously the configuration of the seat and the relative positions of the various moving elements relative to one another.
In addition, the seat control unit has means for managing the control of each of the actuators so as to ensure that certain parts of the seat do not strike obstacles, which could lead to the obstacles being damaged, e.g. when the obstacles are constituted by baggage. In addition, avoiding obstacles serves to increase seat lifetime, by ensuring that the seat does not damage itself by making repeated contact with such obstacles.
Such a seat provided with means for ensuring that the footrest does not come into contact with the floor is described, for example, in U.S. Pat. No. 5,651,587.
In the device described in that document, the seat control unit is adapted to perform various tests directly on the positions of the various actuators.
The tests consist in comparing the values supplied by one or more actuators with a set of predetermined threshold values, the threshold values being defined as a function of the geometrical configuration of the seat so as to ensure that the footrest does not strike the floor.
Although that solution for managing the actuators does indeed make it possible to prevent the footrest from striking the floor, it is extremely difficult to define the threshold values once the seat itself comprises a large number of parts that are movable relative to one another and that are associated with at least as many corresponding actuators.
In practice, the predetermined threshold values are fixed so as to avoid an element striking an obstacle, and for this to be true regardless of the positions of any of the other elements of the seat.
Consequently, very many potential configurations of the seat are forbidden.
An object of the invention is to provide a seat comprising a control unit which is easy to configure while nevertheless giving access to very many seat configurations without running the risk of a moving element of the seat striking an obstacle.
To this end, the invention provides a seat of the above-specified type, wherein said management means comprise:
computation means for computing, in a frame of reference associated with a fixed portion of the seat, the current position of at least one predetermined critical point of the seat on the basis of the current position(s) of the or each actuator, and on the basis of the geometrical characteristics of the seat;
evaluation means for evaluating the current position of the or each critical point of the seat relative to an associated predetermined boundary in said frame of reference and defining said forbidden region; and
control means for controlling at least one actuator independently of the control selected by the user.
In particular embodiments, the seat further comprises one or more of the following characteristics:
said computation means are adapted to compute the current position of the or each predetermined point in a cartesian frame of reference;
said boundary comprises a set of straight line segments;
said evaluation means are adapted to compare a distance between the current position of the or each critical point and said associated boundary with at least one predetermined threshold value;
the seat includes a plurality of actuators and means for tracking the current position of each actuator, and said means for computing the current position, in said frame of reference, of the or each critical point are adapted to perform the computation on the basis of the current position of each actuator;
said control means are adapted to control a secondary actuator different from the main actuator selected by the user in order to move the or each critical point away from said associated boundary whenever the distance between the current position of at least one critical point and the associated boundary becomes less than a first predetermined threshold value;
said control means are adapted to stop the main actuator when the distance between the current position of at least one critical point and the associated boundary becomes less than a second predetermined threshold value smaller than said first predetermined threshold value;
the seat includes means for modifying said predetermined boundary over time; and
said means for modifying said predetermined boundary over time are adapted to modify said boundary as a function of the position of a moving element in the surroundings of said seat.